I haven't saved my hard work, power failure! Is it possible to retrieve it from auto save or backup files?
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Yes. Rename the files.
For example:
If the file name is Game.capx.backup1 then change it to Game.capx
If the file name is Game.capx.autosave then change it to Game.capx
It's all covered in the manual.
Should be enough info for you but if not, just ask.